Delimbing in the logging field comprises removing or cutting off the branches from a felled tree. In the days of old, logging was strictly a manual endeavour and a logger would chop the limbs from a felled tree using a hand axe. The advent of large-scale logging operations has lead to the development of logging machinery to improve the efficiency and output of a logging operation.
In U.S. Pat. No. 4,462,438, Gaudreault discloses a dual head delimber which is mounted to one end of a boom on a logging vehicle. The dual head delimber comprises a cradle having two sets of pivotally mounted clamps which are juxtaposed to one another and mounted at an angle to define a V-shaped arrangement in relation to the longitudinal axis of the boom. The dual head delimber also includes a separate delimbing knife for each clamp. In operation, the operator moves the boom to bring the dual head delimber near a pile of felled trees and the delimber is lowered with the clamps opened around the felled trees. The clamps are then closed to grasp one or more of the felled trees and the boom is retracted so that the butt ends of the trees can also be grasped by another clamping element. The clamps are then slightly loosened and the delimbing knives are brought into contact with the trees, and the boom is moved longitudinally along the trees to delimb the trees. Once delimbed, the first clamps are engaged, while the second clamps are disengaged, and the boom is moved to unload the delimbed trees.
While the dual head delimber taught by Gaudreault provides a means for delimbing trees, there are shortcomings. First, the arrangement of the dual head delimber and boom requires a vehicle with an adequate flat-bed to accommodate the boom and the clamp elements for clamping the butt ends of the trees. Secondly, the felled trees cannot be delimbed as they lay on the ground. The trees must be gathered into a bundle and loaded on the vehicle with the delimber as taught by Gaudreault. In practical terms, this means that such a vehicle will only be suitable for roadside delimbing operations and not in the field. In another aspect, the arrangement of the clamping elements and delimbing knives limits the effectiveness of the dual head delimber, and also the number of trees which can be delimbed at one time.
The present invention addresses these shortcomings by providing a multiple-head delimber apparatus suitable for mounting on a grapple skidder or line skidder, which allows a bundle of felled trees to be delimbed on the ground without the need to move or lift the trees off the ground.